Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate	$ (5,339)	$ (4,473)	$ 20,620	$ 15,848
Income Tax Reconciliation, Differences Regulatory Commission	(381)	(378)	1,202	1,036
Income Tax Reconciliation, Other Adjustments	246	298	(528)	(940)
Income Tax Expense (Benefit)	$ (5,474)	$ (4,553)	$ 21,294	$ 15,944
Effective Income Tax Rate	40.50%	40.50%	41.00%	39.90%